1. Field of the Invention
The present invention relates to a photo-coupler semiconductor device (photo-coupler) and to a production method therefor.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. Hei 11-177124 (1999), for example, discloses a prior-art photo-coupler related to the present invention, which is designed so that light emitted from a light emitting element is received by a light receiving element. The light emitting element and the light receiving element are located in opposed relation on die pads of first and second lead frames, respectively, which are inclined with respect to each other, and encapsulated in an encapsulant of a light-transmitting silicone resin. Thus, at least a part of the light emitted from a major surface of the light emitting element parallel to a mount surface is directly incident on the light receiving element without reflection. The patent publication also discloses a photo-coupler production method, in which the encapsulant is applied over the lead frames respectively mounted with the light emitting element and the light receiving element, then formed into a predetermined shape by gravity and cured, whereby the light emitting element and the light receiving element are embedded in the encapsulant on the lead frames.
With a recent trend toward a higher board mounting temperature due to elimination of lead-containing components, it is indispensable to improve the heat resistance of a package of the photo-coupler semiconductor device. However, the silicone resin to be used for covering the light emitting element and the light receiving element to form a light transmission path has a high linear expansion coefficient, so that the resulting package is liable to crack due to a thermal stress occurring therein when it is mounted. Further, the aforesaid production method involving the embedding of the light emitting element and the light receiving element in the encapsulant is not suitable for mass production, because the shape of the cured encapsulant is unstable.